Rinse-aid composition comprising siloxane surfactants are known from the prior art. EP 875,556 discloses a rinse-aid composition for plasticware, comprising form 0.1 to 10% by weight of the composition of a certain polysiloxane copolymer. The pH of these compositions is not disclosed, neither is the method of making them.
Siloxane surfactants can present super-spreading properties, due to their low surface tension. These super-spreading properties give rise to anti spotting, filming, shine and drying benefits when siloxane surfactants are used in rinse-aid compositions. It has now been found that some siloxane surfactants are easily hydrolysed under alkaline or acidic conditions, thereby reducing their super-spreading performance.
Rinse-aid compositions are placed in the rinse-aid reservoir of a dishwashing machine. These compositions are usually acidic. The user will refill the rinse-aid reservoir when empty or getting low, therefore, any new rinse-aid composition should be at least compatible with acidic compositions in order to avoid the risk of the composition being destabilised if placed in the rinse-aid reservoir containing residues of an acidic composition.
On the other hand, rinse-aid compositions may need to be acidic in order to keep dissolved some of the rinse-aid ingredients.
A problem commonly found in tableware washed in a dishwashing machine, especially on glass items, is deterioration of the glass. The deterioration can be caused by two different mechanisms—corrosion and deposition. Deposition comes from dishwashing detergent ingredients that are deposited on the washed items and not removed during the dishwashing process. Corrosion is thought to happen by dissolution of the glass silica lattice via hydrolysis, accelerated by metal ion leaching due to the builders present in automatic dishwashing detergents. Corrosion can seriously deteriorate the appearance of glass items.
The aim of the present invention is to provide a rinse-aid composition stable under storage conditions, compatible with other rinse-aid compositions and capable of providing glass-care benefits.